Telephone system



Feb. 24, 1931. R. s. Emu-:l ET AL 1,793,582

` TELEPH/ONE SXSTEM Fifled April 1o, 419523 2 Sheets-Sheet l Feb. 24,1931?. R. s. BAILEY ET Al. r1,793,532

` TELEPHONE SYSTEM Filed April 10, 1928 2 Sheets-Sheet 2 gli.

PatentedV Feb. v.24, 1931 Y 'oF NEW .YORK

Y' Application sied Apri11o,

' This invention relates totelephone vsystems and particularly to 'systems ini whichtollcon-` i nections vk are extended* over automatic trunk lines.

' Its.' object Vis to simplifyandimprov'e the equipmentfor-controlling the operation of the automatic switches .used .to extend, the'u trunk,

lines. Y A Y 7.1./ 1 'In the past, trunk f line connections have beencontrolled by' means of signals transy mitted over separatecommon channels -between offices to indiandridentify. the incom-v ing lends off trunksseizedat their, outgoing ends. :L p Y n -This Yinvention `is 'anximproveinent over systems of this typein that it provides means j whereby? trunks between axrst anda second ofice terminating in automatic switches at the secondoice are identified 4andprep`are d forextension to `desired lines in responseito code impulses transmitted tothesecond oiice over a separate common channel on theseizurefof said trunks at the first oiice and-wherebysald automaticv switches .are actuated v:by dialing'V impulses received over the common channel ,tol connect theV seized trunks with the desired lines. Said trunks are also, arranged for two- Wayservice in which theY automatic Switches shows the outgoingend ofa'trunk atV one .oi'ice arranged'in accordancewith this Ainvention mitted over the common channel from'the irstofice.

This invention has been illustrated 1n the accompanying drawings in W'hichzlhgurev 1 and terminating at a toll operators position while Fig. 2 shows the incoming endof thistrunk at a second ofice lterminating Vin a switch having access to trunks leading to other ,oltices A channel has been'shown in these two igures betweenvthe rst and secondv oihces common to a plurality 'of such trunks.v

This channel is arranged toserve inthe establishing of connections over -said trunks in accordancewith thisinvention and `an im- Means is further A figeassza -RANn s. BAILEY;` or criant'v mDGnNEW JERSE'YQAND STANLEY? FQNELSONZ onBRo'oK- Y1.5m, nnwyoax. ANnFRANK n snirnxgon ENGLEWOOD,--1\*TEW JERSEY, Aslsrefnonsfro AMERICAN TELEPHONE ANDVTELEGRARH commun,l A ooRPonAfrioN Y f TELEPHONE sYs'rE'l'vI i .1928. serial No. 268,844.

pulser sending and.- receiving equipment .requiredf-or this purposeavhich is common to ya plurality ofsuch trunks alsorshown atl the twooflices. .n i, l v

' Referring to yfthe drawings the invention operator at anoficeB 4may,xloy insertingthe calling plug'v of; a. cord :(not Jshown) -into fa callingfrj'ack l and '-by operatingfkeysin the, sender 5 equipment C5 establish a" connection l groupof trunks and hunt for aand., connect r group. These groups off trunks may lead lto The seizure-of the vtrunkTloy the operatorlhas? beenaillustra'ted ina system: whereby 'any' trunkT to'an idle trunk, such:ast'llL,` in said Y l different o'iices-,'.tributaryl 13o-office D.' 4';

atA causes the Vsender eoluip'mentl CftoifuncfV tion to'transmita code-signal ove'rthe conivmon signalingchannelM toactuatea switch N to select trunkT andpreparetheassociated switch Sffor `operati'onloy succeeding control `I impulses. Such impulses may he produced' by operation of keys in the sender equipment Y y l @Land-'may betransmitte'd over channel'- M.

`In this sender equipment two keys, i5 Van'df only', havev beenfshown ofa group' of ten *num-f ber keys employed in: theselection of' correspondingl levels in the switchSfwhere'the'ter- 'minals o the. desired lgroup oftrunksareld cated.'A In addition, there; hasn .also *been shown keys KA andiKB'which whenoperate'd causeA the selection 'of corresponding groups y of trunks in the'level selected bythe number' keys. --As soon as trunk Tis seized by switch Ndialtone is transmitted yhack overV the trunk to the operator 'at A to'notify-her tofs'elect the desire'dgroupof trunks -Thejoperator then? sends the fdesiredjnumher by depressing a l numloerfl key and either one of the'A keys and KBfand the switch Sil is accordingly ope*y erated. The tone is removed from the trunk y common. Switch N is, also restored to -normal at this time and the switch Safter have ing been advanced to theproper groupfxof; trunks proceeds to hunt fork an idletrunk in by-the removal of the*answeringplug.`

The trunk T is also made busy and when the idle trunk is found ringing current is transmittedto the tributary officer When the conversation overthis' connection is linished the operator at A removes the calling plug from jack 1 andthe sender G- is then again-seized and acts to transmit ardifthe purpose of restoring the selector S,the switch N and the sender C to normal condition.

D, although: another vco'designal may-,be used,

If a connection. is to beestablished in the'Y opposite direction betweenoiiices D and-'B the-seizure of a'tiunkssuchas Tliatv a tributary o'flicelcauses-the-selectors) or any other idleselecto'r -tobeactuated as a line :finder to over trunlrtT to actuate the supervisory lamp 10 yat oiiiceB toznotifythe operator'atrA-that a connection is' being-established over; .this

trunk; '.AL vbusy signal 11xis also actuated to indicate that thisftrunk is engaged. The operatoratgA will fnowinsert; the answering plug of af cord intoftheanswering Jack lQ and when conversation over this connection is.-

finished itis released bythe operator at A this case the'connection `is restored tor normal in the-same manner as when a connection` Aoriginates atqoflicezB- as hereinbefore described.

The switches and may bei-of the well known Strowger ty-peihavin-gthe usualy upand=around movements. Y

A description will now be-Inade in detail ofthe operation of this I-system. If a connection is desiredfrom officeV B, the toll operator at Ainserts the-*calling plug of a cord (notshown) in jack; 1. This causes the operation of relay -9 over thevsleeve circuit ,inV a mannerwell lknown Vin the/art. Relay 9V in operating closes a circuitfor busy signal 11 `which indicates :to other toll operators that trunk T 'is busy. Relay 9 in operating also closes a connection for the operation of relay 13, from battery, winding of relay 13,

outer right hand armature and'front contacts of relay 9, outer righthand armature and back contact of relay 14 to ground. The operation of relay 13 cuts off the tip and ring conductors of the trunk T from-the answering jack 12and connects them to the, calling ing of'relay 15, lowerinner armature and front contactV of relay 13g-through the outer armature and frontcontactscf relay 9 to the massale The code signal in*` this case has been. shownas the reverse. of the code signal originally produced toV selectlthe'trunk T at oiiice Tny ground at the right hand armature and back contact of relay 14.' It should' be noted that a circuit is also closed from this ground to battery through the winding` of relay 16 but that this winding isv short-circuited through the upper inner armature and back contact -of relay 16, andlower inner armature and back contact of relayl. `Relay 16 willcon- "'s'equently'notfgoperate at `thistimeLy ferent code signal over channel M'to'actuate i the switch N v to vagain Yhd the trunk T vfor theabove mentioned'short-circuit for relay 16 at its' lower armature and back contact.

Relay 16 is therefore now operated and thus removes` the battery at the upper outer armature and back Contact vfor relay 15 causing pends on the slow Y:to 1 release characteristic ofrelay'15 andthe slowl to operate characteristic-of relay 16. This momentary impulse ,ofV ringing currentfrcm source 17 ,causes the operation ,of the f alternating current-V responsiverelay 100. Relay 10.0y closes :an obvious` circuit for the operation of relayf101' which provides'ja ylocking*circuit for itself through its upper armature and frontcontact to ground at the. lower armature and back contactI of. relay 102;-1-1? connection is lalso `established .for the operation ofrelay 10i-3 as follows: Battery, upper winding of relay 103, upper outerfarmature and .back contact of: relay 104,5lowerarinature and front ccn- The .operation tact kofrelay 101 to ground'. of relay 10,3 Vmakes 'the selector busy and thereby preyenls'its operationas a line 'finder on Ycalls incomingy `from tributary offices.

` This is accomplished by transferring the in starting leadv 106- from the win lingV of relay 104C-to the out7 starting lead 106 at the lower armature and a front 'contact of relay 103, through thecontacts of the key 107and thereby'lp'revents the selector switch S Operating as;V a line'iinder but'permits-succeeding selectors in the group to hunt as line' finders for? Vtrunks on` whichV the calls are incoming from tributary offices. The-` operation ofV switch S as a line finder will hereinafter be described. f l Y Referringback to Fig. 1, when relay) operated a circuit was also closed for the operation of the relay: 20 as follows: Battery,

winding of relay '20, lower outer armature and back Contact of relay 21, right' hand outer 4front contacts' and armature of relay 9 to:

ground Vat the outer `right hand armature and' back contact of relay 14.1 Relays 22 and23 lconstitute the usual sequence circuit employed in arrangements where`A common equipments are used, such as sender C com- 1 mon to? a plurality oftrun'lsT, for .connecting the trunks in the order `in which they are seized-to the common equipment ,Theser'e laysA are individua-ltotrunl: T `audit should beunderstood that each-trunk inthe` group isfprovided with corresponding relays. The operation off this sequence e'ireuit is a-s-fol' lowsrRelay 2 0 yin operating closes'a eircu'i` Vt.for the operationof relay22 as follows :'Froni Y battery, through tlielupper inner armatures and 'back contacts ofrelays correspondingtol relay 23of sequence circuits associated with Y trunks of a higher number in the group, wind :ing of relay 22, upper inner armature and back Contact of rela -214 nouer inner arma Vture andfrontl Contact of relay 2 9 to ground.

The. operation of relay 22 closesea Circuit for the operation of relay 23 asfollows: Battery, lwinding of 'relay 23,'inner andlower arma-A ture and front Contact of relay'22 through Y' the make before break conaets of relays `roor#V res ondin to relaI 22 of the lower numbered P g Y trunks in the group. The operation of-both jrelalys 22 and 23 can therefore-only talre place if the common equipment@l isfnot engaged by another trunk. Y

rvYVhen relays 22 and 23 are both operated `a Circuit is closed from batery through a-r-` 25."

sistance 25, windingof relay 2l, lower inner armature and'fron't Contact Vof. relay 20, lower outer armatureand front Contact of relay 22,

.lo-wer inner armature and front contact-of relay y23, to winding ofrelay 26 to ground.

Relay 21 is marginal so that it will-not op-' erate in this Circuit. Relay 26Jhowever op-vv erates and connects battery to the common signaling channel M at its outer right hand armature and back Contact and through 'he .armature and front Contact of relay 27. Re-

lay 26 also furnishes battery for theopera tion of relay 28 over an obvious circuit. Re-

, lay 28 -is slow to operate but prepares a sov circuit for the operation of relay 29. This circuit will Vbe'elosed when the interrupter v30 closes a .connection to ground at brush 3l with the circuit extending through the second inner armature and back eontactof `relay 32, make before break Contacts-of relay 29,

nthe winding of this relay, the armature and front Contact of relay28, inner right hand armature'and front Contact of relay 2 6 to battery. Relay 29 in operating provides a locking circuit for iself independent of in- ,terrupter 30k from ground atthe' lower outer armature andbaek Contact of relay 32. Y The ground at the interrnpter 30 is applied alternate'ly to brushes 3l and 33.

. VWhen relay 29 operates and the ground at the interrupter 30y is' later connected to brush 33a -cireuit isA completed for' the operation of relay 27 as follows; Battery,-winding of relay 27, upper front contacts of relay 29,; Vbrush 33 to ground. Relay?? will new there# fore be alternately operated and: releasediiny der eontrolrofV interrupter 30 andl Cause the battery connection for the commonsignaling channel Mto be corres ondino'l interruatl" ed'atl the armature and back Contact of this relay. It should be noted that the brush -33 `and 43,44 and 45 and 7` armatureand front' Contact of relay 29, brush- 33, interrupter 30 to ground. Relays 35and' 36 areftiieeseeond pair-ofrelays of acount A ingrelay'V system well-lr'nown'in the art. 1A A few of the otlierrelays Hof thisv systeinhave been shown and arefdesignatedlO andf4l 42 understood that there areteny groups of sii'eh eountingrelays assoeiated'with the number and 48. It should bev lreys'in the usual rnanner, although only ve j pairs of relays have-'been shown for the sake of simplicity. "When the ground at the interrupter '30 is removed from brush 33 for the rst'tiine relay 36ope'rates`in series with re-v lay 35 from battery through the windings of these two relays, arniature'and front oontact of relayV 35 to ground at the lower arma# ture and backl `Contact ofrelay *32,5 On the' next oonneetionyof thegroundat the inter rupter '30, relay/'40 operates througlithe arniatureand b'ael.eontaetfof`V relay 41 andA armature andfronteontaet ofrelayV 36. vOn

the nextrernoval ofthev ground'at the in-j terrupter 30, it is obvious that relays 41 and 46 operate in a-parallel Circuit iii series with l relay 40 and lock to lground at the vlower outer armature and back eonta-ct of relay 32. In other Words, it'will require two successive Connections to ground ofthebrush 33`t0 cause these counting relays and rela-y'46 to be operated and locked. It is also evident that relay 27 is operated twice during thisperiod to interrupt the connection, ifroniV Vbattery at .the outer right-hand 'armature and vfront Contact of relay 26, for the common'v signal channel M. Th-e operation; of relay 46 Closes an obvious Circuit for 'aeration of relay 32 through its lower )winding andthis relay in operating provides" a locking' Cir-y cuit for itself through' its' upper winding,

upper armature and front Contact, toground i at the upperarinature and back Contact of replay 33. The operation of relay 32 opens the` looking eireuit forfrel'ays 1.29, 35, 36, 40, 4l and 46l so that these relays vwill now bereleased. Consequently relay `29 Cannot be* vagain operated until relay 32 has released as hereinafter willfbe described. f

Upon the next connection of'ground at the l interrupter 30| to brush 33 ay circuit will now be elosedjfor theoperation" ofrelay 38 as follows: Battery, winding of'relay 38, inaltebefore-breakv 'contacts' of this relay, inner ofrelay 32, brush 33, toground at the interrupter 30. Relay 38` provides a locking` Circuit for itself throughits inner lower arma# `lower armature',armatureand front Contact y ture' and front contact to ground atthe armalows Battery, windingot relay Y24 and its upperlinner armature andback contact, upper4 armature and front contact of relay 38,

upper armature and baclr contact of relay' 32, to ground.. Theconnection from brush 31 on the nextlclosure to ground fronrthe interrupter 30 will know therefore be completed as before atthesecond lowerarmature and. back contact of' vthis relay for the reoperation of relay 29 which locks to the ground at the lower jouterV armature and back Contact of relay 3 2. 0n the next closure of the ground vat interrupter -30 for brush 33 relay 27 will operate as before and a 'circuit impulses respectiyely have, now been sent to the distant office D andthese code impulses will also be completed for theoperation of the counting relay 44 as follows: Battery, windingv of relay 44,'upper armature, and back Contact of counting relay 45, lower mid- "ldle yarmature and front contact of relay-.23,

inner,upperarmature and-back contact of relay 37lower outer armature and front contact of relay 38, right hand armature and loaclrcontact'otl relay 39,-upperarmature and @front contact of relay 29,v brush 33 to ground at interrupter30. On thesubsequent interruptions ofthe ground `'connection from interruptor counting relaysr45, 42, 43, 35, 36, 40, 41and 46 willi operate in succession,

, and relay 27 will ofcourse also be alternately operated and released in accordance with the successive connections to ground through brush 33 frominterrupter 30. Thus theconncction from Vbattery for the common signal channel M will be accordingly interrupted.

Another series of Aimpulses therefore transmitted over this common channel to otiice D and in this vcase the number of impulses will be four, asithe connection originated at the fourth group of countingirelays 44 and 45. lhen this series of impulses has been transmitted relay 46 is operated and relay 32 is again operated. In this case relay 32 is locked by a circuit through its upper winding and upper armature and front contact, upper armature and front contact of relay 38, upper inner armature and afront contactzof relay 24, to ground at the outer lefthand armature and back contact vof'relay 39.. Relay 29 isthereby released 'as well as the counting relays 44', 45, 42, 43, 35, 36, 40, 41 and 46. e

Two series of impulses of two and ifour act in a manner to connect the kcommon signaling channel M toequipments vassociated with the trunkT at this office and caused said equipment to apply a tone to the trunk to notify the operatorfthat she `may (dial the 'number of the tributary ofiice to which a connection is desired.y When battery was rst.: I connected to thechannel M relay 11 0 oper- -1 ated. The-operation of `relay 110- closes an obvious circuit for lthe operationVVV of relay 111 which in turn causes the operation of relay 112. Relays 110 and 111 follow the succeedinginterruptions o f battery on thech'annel M but relay 112 being slow tof release re-y Vmains operated during pulsing. On the first impulse the release ofy relay 111 'causes `the operation of relay 1113 and the Vertical magvnet `114 in series. The .circuit for this magnet and relay `mayiloe v traced from battery,

through the magnet` 114, winding of relay 113,thelower normally closed contacts of' the vertical ofi" normal contacts115,r ight hand armature and front contact of relay 112, armature and back contact of relay 111 to ground, Ther operation of vthe Vertical magnet 114 operates its Vertical ofnormal-P contacts 115 so that the operating path for the vertical magnet 114and relay 113 is now Y contacts of the Vertical-,oit vnormal contacts 115. vRelay 113isj` slow to Lrelease so-thatit transferred through the armature andfront contactot relay `113 fand the; lowerl closed. Q01-"1 will vbe held operated during the pulsing.

The iirstseries of impulses being two in num'- 1 ber causesthe Avertical-magnet 114 to step the brushes of switch Nup 'to thesecondy level of terminals on this switch.

Atthe end of the second impulse relay V111 romains operated until the next series of impulses is received as relay 110 will be 1nain-k tained operated. This affords sutiicient 'time for relay 113 to release and transfer the connection from the armature and bach contact. of relay 11-1 to the wind-ings of relay 116 andV rotating magnet 117 in series.A The next series of impulses will now actuate the ro# tary magnet 117to cause the switch N to step `in a rotary direction Vuntil the fourth set of terminals in the selected level are connected to the brushes ofthe switch. These terminals are shown inthe dra-Wing and marked 120; Relay 116 being slow to release remains operated during the pulsing. The irsttoperation of magnet 117 causes a circuit to be closed for relay 121 as follows: Battery, winding of relay 121, inner right-hand armaturel and front. contact of relay 116, inner lett-hand` armature and4 front contact of relay 112,

armatureand front contact of relay 4111 tov ground. Relay-121 is'locked in operated position through the circuit completed at its:

left-hand armature and front contact to the ground at the outer left-hand armature and front contact of relay 112. At the end of the fourth impulse relay 116 is released and provides a circuit for the o-perationof relay122 as follows: Battery, winding of relay 122, right-hand armature and front contact of relay 121, to ground at the outer right-hand armature and back Contact of relay 116. The

circuit connectionv from. ground at the arinature and front contact-0f relay 1 10 islno-w Y. transferred from relay 111 to the lower brush of switch -N and lower terminal in the fourth set marked v12() in the selected levelthrough .thel winding of rela-y 121l`to batter f'. Relay 111- is therebyreleased but it will Ybe ^noted that relay 112 lis maintained lockedV in itsoperated position through itsl innerf left-hand armature and front-contaron through 'the inner righ-hand 'armature and hack contact of relay 116, the upperk brush of the switch N Y and the upper terminal ofthe set 120, upper armature and back contact of relay 126, lower armature and back contact ofrelay'102, to ground. Y y

The alcove mentioned circuitfor relay 12a causes the relay to. operate and close an ob-` vious circuit for the operationtof.relay-127 and also a circuit for the operation of relay contacts fromgroundand a tonesource 130,`

to the tip yand-ring conductors of trunk T. .As the' trunk is connected through acklto Y the cord-of the operator at A', this tone is rec ofthe fifth level.

ceived at the operatorls `telephone set andnotitles her that the dialing may-lJegin.v The circuitv connections at oiiice-D will.now. remain in this condition until the dial impulses are received.

The operator at A upon receiving .this tone actu-atesthe keys for the selection ofthedesired tributary otlic'e'. Let `it nowbe assumed that the trunks from the desired tributary of-` tice terminate on the second half ofthe fifth levelof the selector S. -The` operatorV at ,A will therefore dial the digits 5 and 6 by depressing the iifth key 1narked-5and key KB. The operationof key 5 causes the switchS to step its brushes to the lifth level andthe operation of key KB causes the `switchto r0- tate its brushes on this levelto the sixth set of terminals in this level, i. e., the -secondhalf As hereinbefore stated `the arrangementl may be such that only twol of this latter type of'keys KA and KB'lare .provided in the sender C on the assumptionthat notmore than two groups of trunks leading to tributary ofces are located in each level of terminals of switch S.

lhen key 5 is actuated the lrelay() operates over a circuit as follows: Battery at the lower armature and frontcontact' of relay 1. vthirdlower armature vand front contact of relay 32, the two windingsy of relay inseries through an upper pair ofinake-.before-break -contacts ofV this relay, the contacts of key` 5 7 the .upper Winding of relay 515 to ground kat the armature and back contact of this relay.

When. relayiO-operates a ...Circuit ,'slQSedfQr the,operation-l of relay: 51 `whichdid not loper-,f

. ate-fin the previously I,tracedcircu-it dueto the high resistance ,of this Icircuit caused by the high resistance of the lower winding ofrelay .50x The newl circuity for relay 51 may-be Y windingsjo-f relay-v 51 'willprevent4 any` vrelay such as, for example, 52 frjorn operating-,while key 5 remains depressedin case anygotherfkey is operated, i; e.', the combined resistance of thesegtw-o,` windings` in serie; With i the VA.high resistance of the twowind-ingsgof any/other relay -would prevent such la-relay-from r.openating as long as key rvremainslcperated in View ofthe comparatively lower resista-nce path to battery provided throughthecontacts ofikey 5and thevupper1 In'akebefOre-b1yeal-,iY

contacts of relay50 Relay. 50infoperating provides: a; locking circuitgfor; itselfto f ground at'the armatureand baclrscontact of relay 49. This circuitmay beitraced from thi-s ground,

through theupper-inner. armature. and front Contact ofl` relay 50,v the-:upper low resistance winding of this relay and its lower-,front con; tacts, through thel winding of relay 39, to hattery, and through' the lower front ,Contacts of relay50 through aresistance to. battery.. atlthe lower armature: and front contact Ifof relay. The lower high resistance windingoffrellay 50 is! .thereby l s'hort-circuited. A Consequently 'imV Y as long as relay- 50 remainsoperated any other relay.v in this group willv be. prevented from operating.v in case theV associated key is: de -y pressed, as-y the two windings in -such a relay will be shunted bythe fconnectionto ground at the'larmatureand baekcontact of relay49 through ythe low resistance windingfof relay 50. Relay 50 alsopreparesa circuit for relay 47 of the fifth'grouprof countingrelaysto brush 33v andthis circuit willbe completed when relayg29 is operated.' and'lbrush 33 is connected to interrupter 30`as will hereinafter be described. y Y, c s I When key KB isfactuated relay 58 is operated as relay 39 is operated at this time; relay f 39 being operated by the circ-uit`completed as described `through the winding ofthis relay on the operation of relay 50. The circuitfor relay 5.3 may be traced as` follows: Battery, innerfleft-hand armature and front contact of relay 39, the highand Alow resistance windings of relayy 531m seriesyupper innerV armaf ture and back contact ofrelay 53,A contacts 0f .key KBgnpper winding of relay 54 and armature` and hack contact of relay 54,` to ground. Relay 53 in operating is locked ,and Short-cir; cuits itsA high= resistance, windingl ande also causes relay 5,4ltooperate Afor thesame 1purgl pose and inthefsame manneras relay 51-'was n loer 'of times, Vnamely iive interruptions inl operated on the operation of relay 50. The sender C is now incondition for transmitting the two series'lot impulses y5an'd2 in sue cession." n f fl I When relay 39 is operated as described alooye it causes vthe'release otrelay 32 due to the 'opening'of the connection at the outer right-'hand armature and hack contact 'ot relay 39.V Relay 32' in vreleasing,completes.a ,circuit `for the operation of relay 5.6 as follows: Battery, winding of relay 56, inner right-hand armature'a'ndloack Contact of relay 56, outer'le't-h'and armatureand front:V

contact of relay '39,upper` inner armature and `frontcontactof relay 24, upper armature and front contact of relay 38, upper armature andihac-lr contact ot relay 32, to ground. Relay 56 in operatingy provides a locking circuit` for itself through its makebeore-brea'k contacts to ground at the arma'- ture and hack contact ot relay 49. -Th`e purpose of the operation of relay 5 6 will become apparent as the description proceeds. Relay 32 in releasing permits the operation vot relay 29 on the next closure of the circuit therefore through the`brush'v31 on interrupter 30. Re- Alay 29. locks upY as hereinbefore described and prepares'a `circuit for counting relay 47 which will he completed on Ithe next closure of the connectionlto "ground through brush 33. This circuit 'may now be traced Vas follows: Battery, winding ot counting relay 47 ,armature and hack contact of counting relay 48, the lead marked 4ro1n the armature of relay 48 which' may be connected to the front-contact'also` marked 4 associated vwith the upper'outerarmature o'frelay '50, through the outer right-hand armatureand back contact olrelay '57,'the upper makebefore-break contacts of relay29, brush 33, to ground at the interrupter 30. On the opening ot this circuit at the interrupter 3() the counting relay 48 isoperated and on the succeeding interruptions kof this circuit the remaining countingrelays are operated` and locked up inv succession' andl'thereloy `permit relay 27 to khe alternately operatedaud released to interrupt the connectionA to'hattery for channel M a corresponding4 nurnsuccession. l n

When relay 46 is'tinally operated circuit is complet-ed orthe operation'o'f relay 57 over a circuit as follows: Battery, winding of relay 57, its make-before-break contacts, outer right-hand armature and-ffront con: tact of relay 56, armature and'front contact fof relay 46, to ,f jround'.` Relay' 57 provides a locking circuit for itself through its inner right-hand armature and front Contact to ground at the armature andloack contact of relay `49.` Relay 32 Aisnow'again operated by the operation of relay46 causing the release otrelay 29 and-'the counting relays,

Thi-srelay locks togrou'ndfover a Icircuit as tollows:gBattery, upper 'winding of relay 32, upper armature and front contact of this relay, upper armature and'A front Contact of relay 38, upper inner armature" and front contact of relay 24, outer left hand armature and front contactsof'relay 39, inner vright Vhand armature and front contact of relay 56,

to lground at the armature and back contact of relay 59. The operation of relay 5,7 transters at the outer right hand armature a connection from brush 33 and the countingk relays through the corresponding front Contact and to the upper outer armature `and front contact of relay 53, and from there through lead marked 6 to the lower counting relay Vof the sixthgroup not shown. The'operation ot relay 57 also applies battery for the operation ot relay` 59over a circuit as follows: Battery, middle right khand armature and front contact of relay 57, winding of relay 59, lower front contacts and upper winding of relay 53, upper make-before-hreak contacts of this relay, armature and back contact of relay 49 to ground. Relay 59 in operating open-s the locking circuit for relay 32 and Contact of relay 39,'upper inner armature and n Afront contact of relay 24, upper armature and front contact of relay 38, to ground at the upper armature and back contact ot relay 32. Relay 60 'provides a locking circuit for itself to ground at the armatureand back contact of relay 49. At thev end of the sixth impulse relay 46 causes the `operation of relay 32 and the releasefot 29 as hereinlietore described. The operationof relay 46 also closes a circuit for the operation ot relay'49 as follows: Battery, right-hand winding of relay 49, left-hand armature and front Contact of re lay 60, armature and lfront contact of relay 46 to ground. Relay 49 provides a locking eir'cuit'fo-r itself to ground at its armature and Vfront contact from battery connected through resistance 25 and winding of relay Y 21, inner lower armature and front contact of relay 20, lower outer armature and Jfront Vcontact of relay 22, lower inner armature and front Contact ot relay 23 and the lett-hand winding oi relay 49. This relay in operating causesthe release ot relays 60, 59, 53, 39, 50, 56, 57, 24, 38 and 32. Relay 26 is also rcleased due tothe low resistanceot the letthand winding of relay 49, and relay 26 causes the release of relay 28 andv opens the circuit to battery for channel M.

Y The effect at office D produced by the two sets `of dial '.impulses' willn'ow be described. Itwill be 'l recalled that the. code impulses place'tone onthe` trunk'T tonot-ify the 0p- 'erator' at A that she maydial .the desired tributary oiii'ceand`prepare-the4 circuits at olice vD forthereception of dial impulses.'V

Y VIt will bei recalled thatJrelay 124'is operated vfront lContact of relay 132, winding of vrelay 126, make-before-break contacts of relay 135,

ves

softhat the firstY release of relay 110, on the rstinterruption of the connection over channel`fM, Vcauses the release' of this :relay and Vthus: completes a circuit for the operation Iofthe'yertioal magnet 130 and the relay 131 asQfollows.: Battery, winding ofthe vertical magnet 130,- winding of relay 131, lower normally made' contacts ofy thevertical off normal contacts 129, `right-hand Yarnniture and'- front contact of relay'127, inner armature yandback` contactfof relay 124 to ground.4

The .operation of the' Vertical magnet operatesthe vertical off normal contacts 129 so that the circuit for the vertical magnet 130 and relay 131 is now'transferred to the armature-'Jandfront contact of relay 131 and the closed lower.' contacts of the group 129. Re-

lay/i131 fisrslow in releasing so that it, is held between .the impulses. The first series of impulses, being six in number, causes the switch S to step its brushes to the sixth level of terminals. At the end of the sixth-impulse relay 110 remains operated until the' next series of'impulses are received. This affords sufici'ent'time for the relay `13 1 to release and transfer' the pulsing connection through the windings of relayY 132 and the rotary magnet 133 nseries; The-next series of impulses therefore causes theV rotary magnet to be actuated to `step-the brushes of switch S vto thefsixth 'group of. terminals in the fifth level,

relay 132.remainingoperated during this Ao'f-'the'brushes on the fifthlevel completes a 'circuit' for the operation of relay 126 as follows :v` Battery, lower outer armature and lower armature and `back contactoffrelay 102, to ground. The purpose ofthe operation of this relay will presently be described. The operation of'relay 132 also'eompletes at its inner lower. armature a. connection'y to ground for maintainingthe relay 112 op 'erated after relay 126 is operatedto remove the original ground for maintaining this relay'operated. Relay126 in'operating pro- ".ides a' locking circuit for itself from battery, through its lower armature and fronti Contact, Vto ground 1 at the'- lower arma- ,tureV baclrcontact of relay 102..: This l ground at the .armaturean'dba-ck Contact of relay 102 is nowathroughthe upper armature and front Contact ofrelay '126.130 the'winding of relay1'35the purposeof'which' will be! come.apparent in the succeeding. description.

At the end of the second series ofi dial im'-V pulses relay 132 isvreleased. and removes-the ground for. relay 112 softhat this relay re.-

leases and causesthe release. of relayv 1,21

which in turn causes the Vrelease Vof'frelay 122.

The release of'relay 112 closes anl obvious circuit for' the operation ofthe release magnet 137, which nowreturns-the switch N to its normal `position so as `toimalre it available for another call. The release'fof. relay 132l also closes acircuitzsfor thezwindings ofrelays 140 and 141, .thepurposezof .which will be presently. described. v

Theterminalls142fand 143 ofall thetrunlrs f of each group are strapped together. except thef terminal ofthe last trunk in each group where'the terminal 142 isopenand terminal 143 connected as shown.J Ify thesiXth trunk now is found busy ground will be connected to the'terminals 142 and :143 ldue -to they operationof relay 145. The. windings of relay 140are wound differentiallyandV connected to the brushes 146 and`'147 in" such a manner f thatwhen ground is .presenten the terminals' 142 and. 143 relay 140 will not operate.l The slow to operaterelay ,141, however, will operate over a circuit as follows :Battery, lower 9oVA armature and front contact' ofy relay"126,v j

lower outer armature and b'ackcontactfof relay 132, upper' armature and back .contact of rotarymagnet 133,` lower armature* and :.bacl

Contact of relay 140, rwindingof relay 1,41', lower outer armature and vback contactzoflre'- lay 135, brush147, terminal 143, innerfrighthand armature and'frontcontact of relay 145 to ground. It should be noted that the winding of relay is also/connected` in series with relay 141 tothe battery at the Alower armature'and front contact of?v relay 126', through the upper armature and front Contact ofire'lay 126 to ground at the lower arm'ature'and'back contact oflrelay 102, but this relay will not operate atthis time as thc winding is shorteircuitedby the ground lat relay 145. Relay 141 in operating provides a ground for the operation of rotary magnet' 133 over'an obvlous `circuit so' that the rotary magnet 133 will step the brushes ofthe switch S fromthe terminals of the busy trunk to f' those ofthe next trunk` in the group. The operation of the rotary magnet 133 'opens the vcircuit for relay 141 at the upper armature and "back contact of this magnet sothat relay l141 will now release. leasing Causes-the release of the :rotary magnet'133. This action will be` lrepeated as long' as the succeeding trunks are'found busy until the last trunk is reached. If the.V last trunkis valso busy aground will be found on The relay 141 inre- "i ,igv'osgsez `the;terminal143 butnotfontcrininal 142. tion fronr the Itone lsource 150; atv thev lower In" this case relay 140; will operate, as `it outer armature and back Contact of thlsrefaster in itsv .operation thanrelay '141, over a circuit as follows: Battery, lower arma.H ure and front contact cfrelay125, lower outer armaturev and front"contact of relay 132, upper Yarmature and back contact of rotary magnet 133, lower winding of relay 140, lower outer' armature and back contact of relay 135, brush 147, terminal143, to ground at relay 145. A The operation of relay 140 thus prevents the operation of `relay 141 on this ground as the 'circuit forithis` relay is opened 'at the lower a 1mature and back contact of relay 140. Relay 140 places ground and atene rfrom the source 150 at theupper armatures and front-'contacts ofthis relay on the tip and ring conductors of trunk T to notify the operator at A in oflice B that all trunks to the tributary office that she hasdialed kare busy. f K

1f a trunlris'found idle in this group no ground will be `present on the terminals 142 or 143 so that re'lays'140, and 135 will operate in series overa circuit as follows: Battery, lower armature and front" contact-of relay 126, lower outer armature and back .contact of relay 132, upper armature and back contact of magnet 133, lower winding of relay 140, winding` of relay 135, upper armature and front Contact of relay y.126,.to ground at the lower armature and back contact of relay 102. Relay 135 in operating causes the o operation of relay 152 over a circuit as follows: Battery, lower winding of relay 152, lower inner armature and front contact of relay 135, to ground atthe'low'er armature and back contact ofrelay 102. The, opera-v tion of relay 135 also opens the connections to brushes 146 and 147 and transfers the locking circuit for relay 126 from the ground at the lower armature and back contact of relay 102 to the ground', throughthe upper armature and front contact ofl relay 135 and winding of relay 153, at Vthe armature'and back contact of relay 154. Relay 153 is operated in this circuit. The operation ofrelay 152 connects the tip and ring conductors of the trunk T at the upper and lower` inner armatures and front' contacts of this relay' to the tip and ring brushes of the switchS. This relay also provides a circuit for the operationl of relay 145 over a-circuit as follows: Battery, winding of relay 145, sleeve .terminal of the selected trunk the corresponding` sleeve brush of switch S the middle lower armature and front contacts of relay 152, to ground at the lower armature and back contact 'of relay 102. Relays 152 and 145 are thereby locked in operated position independent of the original energizing circuit for relay 152. Relay 145 in operating connects ground to the terminals 142 and 143 thus making the selected trunk busy.

Relay 153 in operating opens the connecayto prevent busy tone from bcingftran'snntted to the operator at A. when yrelay140 operates.

'rent from the source 156 vto the trunk leadin to the .tributary otce, at theupper outer and inner lower armatures and front contacts of this relay, indicating to the distant tributary officeoperator that a connection-iSy desired over this trunk.. Relay 153 further provides an obvious circuit fortheoperation of` relay 154. The operation of this relay causes the release of relays 153 and 126; rlhe release ofrelay 153 removes the ringing current from the trunkVV while' the release of relay 126 causes thev release of relays 140 and 135. The release of relay 153 causes the release of relay 154. Y :The circuits as'now arrangedV remain in thisv Vcondition during the talking period. That is, the conditions are.

lsuch that a clear'eonnectionl ist-Established over the tip and ring conductors of'trunks TL and T from the tributary oilice tothe operator at A and conversation may'begin as soon as the two voperators have extended the talking connection to the calling and called subscribers in a manner wellknown in the art.

fWhen the conversation is ended and disconnection is desiredthe operator at re*- nieves her plug fromthe jack l causingthe Vsender equipment C is thereby seized and acts as hereinbefore described to send two series of impulsesover the common channel M to actuate the switch N to seize trunk T for the purpose of releasing the connection. However, the orderof the digits in Ithe ycode will be reversedon account of the fact that relay 37 will operate at this time .over a circuit as follows: Battery, winding of relay 37, upper outer armature andfront contact,v of relay 23, upper outer armature and front contact of relay 21, upper outer armature and back contact of relay 20, toy ground. In this case, therefore, four impulses will be transmitted irst followed kby two impulses. r)The operation of relay 37 accomplishes this by switching theconnection from the count- Y ing relays 35 and '44 at the upper inner arma- This relay also applies Vringing 70 Y beenstepped to the ffiourthlevel,r When this level is reached ground on terminal 1 63v will he connectedto brush 168 for the completion of a circuit for relay 166 as follows z;

Battery, second upperg'varmature and. back contact of relay 103,'lower'winding of relay 165, armature and backcontact of rotary magnet 133, third upper armature and front" contactofrelay 104, lupper winding of relay 166, brush 168, terminal 163 and ground at the left-hand armature and kfront contact front Contact oi relay 104, upper ,outer armature and'back contact ofgrelay 103, winding ofthe-vertical magnet 130,.to battery. f Thel of'relay 161. Relay`166 in operating provides a locking circuit for itself to ground at the upper armature and front contact ofrelay 104, the-lower high resistance winding of relay .166, the inner upper armature and` vertical; magnet'releases at.l this ,time due to the highfre'sista'nce of the-lower winding oi:

relay 166 in the above mentioned circuit. Y The operation of relay 166 transfers the stepping circuit from vthe vertical to the rotary magnet at the upper armature and front Contact of this relay so thatfthe circuitfor the rotary magnet will now be traced from battery, throughlthe winding of magnet 133, upper armature and frontcontactof re,- lay 166, armature and yfront Contact orelay 165, to ground at .thesecond upper armature andfront cont-actjof relay.1104..-Relay 165 andthe rotary magnet 133fwllfno'w` alternatelyo erate andrelea'se Keach other toistep switch in a rotary direction-until battery is found on the terminal 17 Oassociated with trunk TL, this battery being suppliedat the outer left-handarmature and ront contact of relay 159. When this vbattery connection minal 170, the correspondingbrush of switch S, upper winding of relay- 152, upper Winding of relay 165, to ground yat the second upper armature kand front contact of relay 104. Relay 152 is locked over alcircuit as herein e- Lfore traced which is completed to the lower armature and back contact of relay 102 to ground: Relay `'152 in operating closes the talking connection rfrom trunk TL to trunk T and also causesthe operation orelay 145 over a sleeve circuit under the control of the connection to ground atV the relayr 102.

' Relay 103 is'also operated by the operation of relay 152 over a circuit as follows Battery,

upper winding 4of relay 103, lower outerV armature and front contact of relay 152, to groundfat the upper closed .contacts of the vertical off normal contacts 129. Relay 103 .the:operationoitrelay 64 which-n turn causes urea-58a? in operating makes switchS-busyas herein' before described while the operation ofrelay 145-causes .the release of relay 159 and conc nectsterininals 142 andg143 to ground tomake the trunk ,TL busy lor calls in the opposite direction.Y The release ot relay 159 causes.` the release of relay 161 and this relay in turn'.v causes the `release oi'- relay 165, while thel operation of-relay 103,causes the release of-V vrelays166- and104. The rotary magnet is.v

also released at this time but no further stepping occurs vasthe operating circuit for relay 165 is broken.V Relay 104m releasing causes the release of relay 164 to-remove the ringing current from the line. f

When ringing current was appliedto the trunlr -T the alternating currentr responsive relay E52 at `Qfice B Ywas operated.- -f'lhe operal tion'of'this relay closes an obvious circuit for lamp`10to be lighted toindicate tothe opv erator at A that a connectionover this trunk is desired. Relay 64 providesa locking circuitfor itself to ground at the outer righthand armature and back contact of relay 14.

operation of relay 64 over an obvious circuit. VVlhen the .operator Arinserts'an answering` plug into answering'jaclr 12 relay 14 is.

Y The busy signal 11 vis also operated by the 64 and extinguishes the: lamp 10. Theopera a tion orelay' 14 also opens the alternating current y bridge for relay 63. i An operating circuittor relay 65 is closed by ,the operation oi relay 14`and this relay isz locked by av circuit v controlled'by relay 21. The purpose of the operation'of relay 65 will become apparent as the. description proceedsl Conversationmay now take: place overY the established connection. y.

l/Vhen the operator removes the answering Y plug from-jack 12v at the end'o conversation relay 14 is released causing the release of the Vbusy lsignal l11 and closes thealternating current'bridge for relay 63. It also provides a ground connection through the lefthand armature vand front Contact of relayv 65 for the operation of relay 21 over acircuit extending through .resistance 25V to battery. Relay 21 in operating causes the release of relay 65 and causes a release signal to he sent to oiiice D in the same manner as hereinbefore described, this release signal causing the release of switch S as her-einbefore described. When this release sig-nallias'heen. sent relay 21 releases and the circuits are then returned to normalcondition.

Itshouldbe understood that while the'invention has been described only `inconnection with lone trunkingrsystem, it, is notlimited by this disclosure but may be applied. to other trunking systems.

What is claimed is: v

:1. In atelephone-system', Aa. irst'moicdfa i essaies second office, lines extending between said offices, automatic switches at the second office'.

for further extending said lines, a single circuit common to said lines'extending between said offices-and means controllable over-:said

circuit for actuating and releasing' said switches. Y Y v 2. In al telephone system, a first ofce,` a

V'from said second-'oi'ficmand means whereby said switching mechanisms serve as selectors .in connections originating Yfronithe first V.second office, lines extendingbetweenftheY `office and as line finders in connections orig#v inating :from said outgoing lines.

8V. In a telephonesysem, a first office, -a-

second office, lines extending between said offices, lines outgoing from said secondoice, automatic switches at the second. office for establishing connections between lines from the i first ofHce andsaid outgoing lines utilized as selector switches for connections origif-A 'Y nating from the first ofi'iceaiid as line findout-going lines, and means including a sep arate signaling 'channel extending betweenl the first and second offices for controllingy ers Yfor connections originating `Vf i'omsaid the establishing and the release" of conne'cl tions of the first mentioned type and for the release of the second mentioned type of conil nections. Y

In a telephone system, a first office, a

first and-the second offices, lines outgoing from lthe second office, automatic switches at the'second office for establishing connections between lines from the first office and said outgoing lines, a separate signaling channel extending between. the first and the second offices, means utilizing said signaling channel for controlling the establishing and the j release of connections originating from ;the s Vfirst office and for controlling the releaseot connections originating from said outgoing lines.

5 In altelephone system, a first' ofhce, a'

` second oce, linesbetwe'en the first and the second offices, lines outgoing from 1he second office, automatic switches at the second office, a single circuit common tosaid lines between the first and second offices, means for transmitting impulses over saidcircuit, and mea-ns responsive to said impulses for' actuating said switches to establish connections' between lines from the first office and said outgoing lines and for releasing said switches.

6. In a telephone system, a first 'ofiice, a secondV office, other. offices, lines extending VVbetween the first and second offices and from Wa ches at ks Seconclwofces, means for'. mtting 'e impulses .over i. Said channel troinpsaid line from the fir tjocejand the-associate(` automatic switch, means .f mltting su .tch setting' first o', and ineans atthe second .officeY reotlierteticea .ante-1 Secondoffibesaches-. socrate wi ialine. rriietheirsftaisep @irate Signaling. channel between. the first and ,tbefseccnd 'oiicerespoiislvete for selecting a .correspioni not' "thereafter t'rans-l inpulses from said Y sponsive to said later impulses for actuating the selected automaticv switch to establish a connection between thel associated line and im,A

a line leading to a desired one of said other` l 7. .In a vtelephone system, a first-office, a secondoffice, lines extending between the 'first and second oices, lines .outgoing from'the lsecond office, automatic switches-at said second oce each associated with a line from the first office, a separate signalingfchannel f between the first and' vsecond offices, means for `tmnsinitting code impulsesover said channel from said first office,nieans at theV second office responsive to said impulses for selecting a corresponding-line 1from the first office and vthe Vassociated.automatic switch,

vmeansfor thereafter transmitting operating yimpulses from said first office, means at the "second-office'responsive to said operating impulses for actuatingthe selected automaticiV switehto"establishr a connection between theY associated li'ne and .an-outgoing li ne,andv fmeans at the second ofice responsiveto code impulses received from the vfirst office for releasing the automatic switch employed inf said connection;

8. In a telephone system, afirst office, a

second office, 'lines' extending .between said, offices, automaticV switches at the second office forfurthernextending saidlin`es,a single conductor common tosaid lines extending between s'alid offices, and meaiisf'controllaible over said conductor for aotuatingand releas-l -ingsaid switches. -l I 9. In a telephone system, a first`office,a

second office, linesf extending vbetween said offices, an automatic switch atthe second office for each line, a singlecircuit'comin'on tof Said lines extending between` said offices,

means responsive to the seizure of aline atA the first office for enabling'. the controlof the corresponding switch at theV secondl ofice over said circuit and means responsive lto theV release of said line alt the first office for controlling said switch over said circuit to cause it to release.

10. In atelephone system, a first office, a

second office, lines.v extending betweensaid offices, -anra'utomatic switch at the secondV office for each line, a singlecircuit common to said lines extending between said offices, means responsive to theseizure of a line at 1on1 i switch at the secondl office oversid crult,

f-*a-nd meanS responve totherrelease of-sad Y Aprn, 1928.

line at the flrst' VOce for controlling said In testimony whereof, We have signed our names togths specificatie*riv this 9th laqy of RAND SQBAILEYQ- STANLEYENELSON. FRANK F. SVHIPLEY.

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